Field of the Invention
The present invention relates to an exposure apparatus, an exposure method, and an article manufacturing method.
Description of the Related Art
A projection exposure apparatus for transferring a pattern formed on an original plate (a reticle or the like) to a substrate (a wafer or the like on a surface of which a resist layer is formed) via a projection optical system is used when a semiconductor device or the like is manufactured. Typical types of projection exposure apparatuses include a step-and-repeat type reduction projection exposure apparatus (stepper) and a step-and-scanner type scanning projection exposure apparatus (scanner). For example, the stepper reduces a pattern of an original plate and projects the reduced pattern on each of a plurality of exposure regions (shot regions) on the substrate. However, when the substrate is tilted or a thickness of the substrate is not uniform, deviation (defocus) between the positions (heights) in the Z-axis direction (an optical axis direction of a projection optical system) of the shot region and the exposure focus occurs. It is necessary to perform focus drive for every shot region to prevent an exposure defect due to defocusing, but throughput is degraded when a time period necessary for focus drive is lengthened.
Therefore, an exposure method of shortening a time period of the focus drive is disclosed in Japanese Patent Laid-Open No. 2001-93813. In the exposure method of Japanese Patent Laid-Open No. 2001-93813, the height of the shot region is also measured when an alignment mark of a sample shot region is measured and the height of the substrate is adjusted simultaneously with the alignment adjustment on the basis of a measured value simultaneously with X-Y movement between exposure shot regions. Also, an exposure method of separately performing global leveling and chip leveling and returning to an orientation after the global leveling by adjusting the height of the substrate according to a leveling correction amount of a previous shot region before the chip leveling of the next shot region is disclosed in Japanese Patent Laid-Open No. H8-227854. An exposure method of calculating a correction value of focus adjustment for each of a plurality of shot regions of a second substrate is disclosed in Japanese Patent Laid-Open No. 2014-99562. In the publication of Japanese Patent Laid-Open No. 2014-99562, the correction value of the focus adjustment is calculated using a measured value of a height measured in each of a plurality of shot regions of a first substrate and a difference between measured values of heights measured in predetermined (single) shot regions of the first and second substrates.
However, when an accurate height of each shot region is desired to be measured in the exposure method of Japanese Patent Laid-Open No. 2001-93813, it is necessary to increase the number of sample shot regions in the alignment process and a measurement time period is lengthened, which degrades throughput. Also, when the unevenness of a substrate surface increases in the publication of Japanese Patent Laid-Open No. H8-227854, a drive amount for returning to the orientation after the global leveling for every shot region increases and the throughput is likely to be degraded. On the other hand, in the exposure method of the publication of Japanese Patent Laid-Open No. 2014-99562, the correction error may increase due to the unevenness or tilt of the substrate surface because the correction value is calculated using the difference between the measured values of the heights in the predetermined shot regions of the first and second substrates.